This invention relates to apparatus for recording operating conditions of a motor vehicle for later analysis, and is particularly directed to apparatus of the type capable of recording braking conditions. The invention is particularly applicable to vehicles equipped with antilock braking systems.
The construction and operation of antilock braking systems are well known in the art, and one of their operating characteristics is that, in the event of an accident, it is generally not possible to examine the vehicle or the accident scene to determine whether the brakes had been applied immediately prior to the accident. This becomes an important consideration when it is necessary to make a determination of fault in causing the accident.
Just as in the case of the well-known flight recorders present on aircraft, there are available so-called drive recorders for automobiles which, for example, log the driver's movements, as well as those of the vehicle prior to and during an accident. Sensors of a wide variety of types can be mounted at varying locations in the vehicle and using a data logger the drive recorder apparatus logs, for example, the last 25 seconds of the driving event prior to a sudden external impact.
In order to record the kinds of conditions which would indicate when brake application occurred prior to impact or the like, a drive recorder, such as that described hereinabove, could be used on a vehicle. However, the use of relatively complex and sensitive instrumentation of this type is highly disadvantageous when the difficulties it must undergo during routine operation are remembered. Such a device must be capable of operating reliably during the entire life of the vehicle, often under extreme operating conditions including extreme heat and cold, as well as strong impact acceleration or deceleration. It is unlikely that any such device will be maintained regularly during the operating life of the vehicle. Especially in view of the latter condition, it is unlikely that reliable storage of data can occur in the event of an accident. These difficulties might be overcome, but they can be overcome only with the use of relatively complex instrumentation constructed at relatively great cost.
It is, therefore, an object of this invention to provide apparatus which is of simple construction and with which the operating conditions of a motor vehicle, particularly the braking conditions, can be recorded with a high degree of reliability.
It is another object of this invention to provide apparatus which meets the foregoing object and which will provide an indication of braking conditions even on those vehicles equipped with antilock braking systems.